Field of the Invention
The present invention relates to an image pickup device, such as a CCD or CMOS image sensor, a control method therefor, a storage medium storing a control program therefor, and a signal processing device for the image processing device, and is particular, relates to the image pickup device having unit pixels, each of which has pixels of different sensitivities, arranged in a two-dimensional matrix form.
Description of the Related Art
Conventionally, there is a known image pickup device that composites outputs of two or more pixels of different areas and outputs the combined signal as a signal of one unit pixel in order to expand a dynamic range (see Japanese Laid-Open Patent Publication (Kokai) No. 2010-283573 (JP 2010-283573A)).
FIG. 10 is a view showing a pixel arrangement of the image pickup device described in the above-mentioned publication.
As shown in FIG. 10, a unit pixel consists of two pixels that are different in area, and a plurality of unit pixels are arranged in a two-dimensional matrix form. A unit pixel 1103 is provided with a high sensitivity pixel (HIGH) 1101 and a low sensitivity pixel (LOW) 1102. A dynamic range is expanded by compositing or selecting the outputs of the high sensitivity pixel 1101 and low sensitivity pixel 1102.
On the other hand, in an image pickup apparatus, such as a digital still camera, it is known that an output of the image pickup device is affected by shading caused by peripheral darkening of an image pickup optical system, unevenness of sensitivity of an image pickup device, etc. Shading correction may be performed so that brightness of the whole image becomes uniform in order to prevent such shading. For example, a conversion property that converts an image obtained by photographing a uniform luminance surface that has uniform luminance distribution into a target output (i.e., an image) is found beforehand. At the time of photographing, shading of an image obtained by photographing is corrected using the conversion property concerned.
Incidentally, in the image pickup device shown in FIG. 10, the centroid position of the high sensitivity pixel differs from the centroid position of the low sensitivity pixel. Accordingly, shading correction data at the centroid positions of the high sensitivity pixels and shading correction data at the centroid positions of the low sensitivity pixels are needed in order to perform the shading correction with sufficient accuracy. Accordingly, the data volume for the shading correction becomes huge, which requires large memory capacity and increases processing load.